Tutorials
Tutorials list >> Pixel art glass ball
Steps
Choose a palette (five colors are enough for a small sized ball: white, a bright tone for the highlights, the basic color, and two darker ones for the shadows and outline).
Draw a circle and fill it with the basic color you picked.
Apply a white highlight. (If the glass ball is part of another picture, be careful to respect the light orientation.)
Add shadows in a circle around the highlight.
At the opposite of the white zone, add a curved highlight using the softer bright color.
Examples of other sizes:
